NAM

The NAM (North American Mesoscale) model runs at higher resolution than GFS (12km vs 25km) and is specifically tuned for North America. It excels at short-range detail — frontal passages, convective initiation, and terrain effects.

Use NAM when: You need to know *exactly* when a front passes your barn in the next 84 hours. GFS might say "Thursday," NAM will say "Thursday afternoon between 2-4pm."

NAM's weakness: It only goes out to 84 hours (3.5 days). For anything beyond that, you need GFS or GEFS.

For equestrians: NAM is your "should I ride tomorrow" model. GFS is your "should I enter that show next weekend" model. GEFS is your "can I trust any of this" model.

Because NAM has higher resolution, it picks up terrain effects that GFS misses — mountain/valley winds, sea breeze fronts, and localized convection.

What NAM does better: - Timing of frontal passages (±2 hours vs GFS's ±6 hours) - Thunderstorm initiation (where the first cells fire) - Temperature inversions in valleys - Lake-effect precipitation - Sea/land breeze boundaries

What NAM does worse: - Extended forecasts (caps at 84h) - Large-scale pattern changes (GFS handles these better) - Sometimes "spins up" too much convection (predicts storms that don't materialize)

Practical tip: If NAM and GFS agree on timing for the next 48 hours, that's a high-confidence forecast. If they disagree, NAM is usually more accurate on timing but GFS may be better on intensity.